function SwapImage(TargetId, ReplacementPic) {

        if ((FoundObj = FindObj(TargetId)) != null) {
            FoundObj.src = ReplacementPic;
        }
}

function FindObj(obj_id) {
    // search for TargetId (alias obj_id)
    var doc,  FoundObj;

doc = document
FoundObj = doc.getElementById(obj_id)           //Netscape 6+ and IE 5+
if (!FoundObj )  FoundObj = doc.all[obj_id]     //IE 4 
if (!FoundObj )  FoundObj = doc[obj_id]         //Netscape 4 good - luck with this Netscape 6.1 doesn't even work
return FoundObj;
}